1. Field of the Invention
The present invention relates to a driving apparatus which uses an elliptical vibration of a transducer to drive and move a mobile body in a predetermined direction, and an image pickup apparatus, such as a digital camera, which uses the driving apparatus to correct a blurring motion.
2. Description of the Related Art
Conventionally, a camera, for example, is known as an image pickup apparatus having a function of correcting a blurring motion. As the blurring-motion correcting function of the camera, an image stabilizing function is known in which a blurring vibration in a pitch direction of the camera and a blurring vibration in a yaw direction of the camera are detected by using a blurring motion detector such as an angular velocity sensor, and an image pickup element or a part of an image pickup optical system is shifted to negate the blurring motion, based on the detected blur signal, independently in the lateral direction and the vertical direction in a plane perpendicular to an imaging optical axis, so that a blur of an image on an imaging area of the image pickup element is corrected.
In an image stabilizing mechanism which realizes the image stabilizing function, a driving unit which moves, to correct a blurring motion caused by a hand movement, the image pickup element itself or a part of an imaging lens in the lateral direction and the vertical direction in the plane perpendicular to the imaging optical axis is used. To operate by following the blurring motion caused by a hand movement, the driving unit is required to have a high response performance, an accurate driving (a minute driving), and a self-retaining capability by which a position of a mobile body is retained even when a power source is turned off.
In response to such requirements, an image stabilizing mechanism using an impact actuator is disclosed in Japanese Patent Application Laid-Open No. 2005-331549. Further, a vibrational-wave linear motor in which two transducers which generate an elliptical vibration on its surface are pressed with respect to a shaft, and the shaft is linearly driven with respect to the transducers is disclosed in Japanese Patent Application Laid-Open No. 2006-67712. In a driving mechanism using the vibrational-wave linear motor, the shaft having a column shape is relatively moved by the transducers, a lens frame is driven by a protrusion provided to the shaft, and the moving direction of the lens frame is guided and moved by a guiding mechanism provided for the lens frame.
However, though the high response performance, the accurate driving, and the self-retaining capability can be obtained in the image stabilizing mechanism using, as the driving mechanism, the impact actuator disclosed in Japanese Patent Application Laid-Open No. 2005-331549, there is a problem that a high output cannot be obtained in a small size since the driving is realized by using an inertial force. This stabilizing mechanism is not suitable when the driving target is an image pickup unit which is comparatively large and heavy, being integrally formed with a dust-proof filter and the like at an anterior surface of an image pickup element such as a CCD in a camera and the like, for example. To increase a driving force, inertia mass needs to be increased and thereby the size of the driving mechanism itself becomes large. Further, due to a principle that the driving is realized by the inertial force which overcomes a frictional force, there is a fundamental problem that an energy loss is inevitably caused due to a frictional sliding and thereby the efficiency cannot be increased so much.
On the other hand, in the so-called vibrational wave motor using the elliptical vibration of a transducer, the efficiency is high and a large driving force can be obtained easily. Therefore, it can be said that the vibrational wave motor is suitable for driving the image pickup unit or the like which is comparatively large and heavy. However, it is necessary for generating a large driving force to press the transducer with respect to the mobile body with large force. Therefore, when the rigidity of the mobile body is poor, there occur problems that the mobile body yields to the pressing force (since the vibration of the vibrational wave motor is originally as small as about several micro meters, a flexure of only several micro meters matters), the efficiency of the driving mechanism deteriorates, and the driving mechanism becomes inoperative because the driving force is absorbed in an extreme case. To prevent such problems, the column-shaped shaft as the mobile body which directly contacts the transducer is formed to have high rigidity, and is configured to transmit the driving force via a protrusion and to move the lens frame as a target to be actually moved, as shown in Japanese Patent Application Laid-Open No. 2006-67712. In this configuration, there are problems that a mechanism of transmitting the driving force to the lens frame side and a guiding mechanism for the lens frame side are required separately, and the mechanism becomes complicated, large, and heavy. In this respect, the moving target itself such as the lens frame may be configured to have high rigidity and may be directly driven by the elliptical vibration of the transducer. However, since any shape and material have own peculiar resonant frequency, it is necessary, against a demand for downsizing, to make the mechanism grow in size and weight more than necessary to prevent a trouble of causing a peculiar vibration and the like when the elliptical vibration from the transducer is transmitted as the driving force.